Is it possible to use --noarp with some connections but not others?

pogeymanz · 2012-07-03 02:28:06

I use NetworkManager to wirelessly connect to several networks. My home network probably doesn't need arp probing, but I also connect at my University, which probably does need arp probing.

Gcool · 2012-07-03 08:20:47

I don't think that's going to be possible. The arp probing in essence will be done by dhcpcd, so unrelated to any connection profile.

So all in all, I would just leave it as is. Arp probing will most likely be useless on your home lan indeed, but it'll cost you a few seconds at worst to get a dhcp lease; so not the end of the world I reckon.

pogeymanz · 2012-07-03 11:51:49

No, it isn't the end of the world, but it's annoying.

My wife's Win7 laptop is connected pretty much instantly when it is awoken whereas mine takes about 10 seconds. I guess Microsoft is doing noarp which is the impolite way.

I also don't think Macs do it either, which makes me wonder if there is any point in worrying about doing arp probing. I mean, probably 90% of the computers on the department's network are OSX or Windows and if they don't do arp probing, why should I? They could still mess up my connection...

Oh well, I'll probably continue being the nice guy. :-)

R00KIE · 2012-07-03 13:26:47

Both windows and osx do a few things that can cause problems, they do what you say, they assume that you will connect to the same network you last connected and try to use the same configuration, they try to skip most steps like dhcp and arp and it will probably work fine if it actually is the same network and no one else got the same IP otherwise they will have to go through all the steps.

I have seen a blog post describing the differences a while ago but now I can't find it and I don't remember how I got there, I guess that if you search long enough you might stumble upon some description of this. From what I remember, the short story is that on linux programs go by the book and try to be good neighbors, windows and osx don't and they can cause trouble just for the sake of shaving a few seconds of the time to get connected, the thing is most of the times it works fine

debdj · 2012-07-03 13:46:17

Would adding permanent entries in your arp cache help better the situation?
If the IP addresses dont change within the lan, it probably wont need arp probes again.

Strike0 · 2012-07-04 21:18:38

What makes you certain that it is the arp requests? Do you see in dmesg that dhcp takes up those seconds to rebind after wpa_supplicant completed?

pogeymanz · 2012-07-05 12:26:58

Nope. I haven't actually tested if it's dhcp taking up that extra time. It's a common complaint, though.

Also, debdj, how does one make permanent entries in the arp cache? Is it just arp -s? Does that need to be run every time you log in?

debdj · 2012-07-05 13:13:06

pogeymanz wrote:

Also, debdj, how does one make permanent entries in the arp cache? Is it just arp -s? Does that need to be run every time you log in?

form man arp :

Each complete entry in the ARP cache will be marked with the C flag.
Permanent entries are marked with M and published entries have the P
flag.

Although am not sure if that would be persistent only across a session or boots.

Arch Linux

#1 2012-07-03 02:28:06

Is it possible to use --noarp with some connections but not others?

#2 2012-07-03 08:20:47

Re: Is it possible to use --noarp with some connections but not others?

#3 2012-07-03 11:51:49

Re: Is it possible to use --noarp with some connections but not others?

#4 2012-07-03 13:26:47

Re: Is it possible to use --noarp with some connections but not others?

#5 2012-07-03 13:46:17

Re: Is it possible to use --noarp with some connections but not others?

#6 2012-07-04 21:18:38

Re: Is it possible to use --noarp with some connections but not others?

#7 2012-07-05 12:26:58

Re: Is it possible to use --noarp with some connections but not others?

#8 2012-07-05 13:13:06

Re: Is it possible to use --noarp with some connections but not others?

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